Steam turbine installation and associated operating method

ABSTRACT

A steam turbine installation ( 1 ), especially for electricity generation, includes a steam path ( 2 ) in which a steam generator ( 4 ) and a steam turbine ( 3 ) are arranged. In order to reduce the risk of erosion for components which are arranged in the steam path ( 2 ), for example blades of the steam turbine ( 3 ), an inertial separator ( 6 ) is arranged in the steam path ( 2 ) between the steam generator ( 4 ) and the steam turbine ( 3 ).

This application is a Continuation of, and claims priority under 35 U.S.C. § 120 to, International application no. PCT/EP2007/050730, filed 25 Jan. 2007, and claims priority therethrough under 35 U.S.C. §§ 119, 365 to Swiss application no. 00531/06, filed 31 Mar. 2006, the entireties of which are incorporated by reference herein.

BACKGROUND

1. Field of Endeavor

The invention relates to a steam turbine installation, especially for electricity generation.

The invention also relates to a method for operating such a steam turbine installation. Furthermore, the invention relates to a use of an inertial separator.

2. Brief Description of the Related Art

A combined gas turbine-steam power plant for electricity generation is known from CH 653 097 A5. Such a combined cycle plant includes, on the one hand, a gas turbine with an associated compressor and an associated combustion chamber, and also, on the other hand, a steam turbine with an associated steam generator. In this case, the steam generator is heated with the hot exhaust gases of the gas turbine.

In the case of the known combined cycle plant, the combustion chamber is equipped with a fluidized bed. The exhaust gases, or flue gases, which are created during operation are laden with particles. In order to avoid entry of these particles into the gas turbine, a plurality of cyclone separators are arranged in the exhaust gas path upstream of the gas turbine.

A gas turbine installation is known from DE 198 34 376 A1, in which stator blades are cooled with a cooling gas. In order to separate out dust from the cooling gas, an axial cyclone is arranged in the cooling gas path upstream of the stator blades which are to be cooled.

With modern steam turbine installations, there is the trend to increase the steam temperature and the steam pressure at the inlet of the steam turbine in order to achieve higher levels of efficiency as a result. With inlet temperatures of 580° C. to 600° C., these steam turbines no longer operate hypercritically or supercritically, but already ultra-supercritically. Newer steam turbine installations tend towards even higher inlet temperatures of 620° C. to 650° C. For future installations, even inlet temperatures of 700° C. to 720° C. are envisaged. It has been shown that at these high steam temperatures, the oxidation of the steam-conducting components, for example of the steam generator, increases superproportionally. As a result of this, oxide particles are created which become detached and are entrained by the steam flow. The particles thus get into the steam turbine, but, as a result of inertia, cannot follow the deflections of the steam flow along the blades, as a result of which they impinge upon stator blades and rotor blades. With the prevailing high velocities, it leads to erosion phenomena on the blades. Such erosion phenomena have a negative effect on the aerodynamics of the blades which leads to a reduction of the efficiency of the steam turbine.

SUMMARY

The invention attempts to provide a remedy for this. One of numerous aspects of the present invention deals with the problem of showing a method for a steam turbine installation of the type mentioned in the introduction, which especially reduces the risk of erosion of the blades of the steam turbine as a result of oxide particles.

Another aspect of the present invention is based on the general idea of removing the entrained particles from the steam flow in the steam path upstream of the steam turbine which leads from the steam generator to the steam turbine, specifically preferably by an inertial separator.

The use of an inertial separator, which in particular can be designed as a cyclone separator, is a comparatively inexpensively realizable measure which is characterized by a comparatively low pressure loss compared with the use of conventional filters. Furthermore, the use of an inertial separator is considerably more cost-effective than the use of high-purity water for reducing the oxidation effect of the steam, or than the use of especially high-value materials in the region of the steam generator for increasing the oxidation-resistance of these components, or than the use of especially high-value alloys or coatings or surface treatments of the blades for improving the erosion-resistance of the blades. In comparison to these alternatives, the inertial separator is therefore characterized by an extremely low pressure loss and also by an inexpensive realizability. An inertial separator is characterized in that a flow deflection is forced within it, which the entrained particles cannot follow on account of their greater mass. Instead of this, the particles impinge upon corresponding obstacles, as a result of which they are additionally braked.

Further important features and advantages of the present invention result from the drawings and from the associated figure description with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred exemplary embodiment of the invention is shown in the drawings and is explained in more detail in the subsequent description, wherein like designations refer to the same, or similar, or functionally the same components. In the drawing, schematically in each case,

FIG. 1 shows a much simplified, circuit diagram-like schematic representation of a steam turbine installation,

FIG. 2 shows a partially sectioned simplified side view of an inertial separator, and

FIG. 3 shows a partially sectioned perspective view of another inertial separator.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

According to FIG. 1, a steam turbine installation 1 exemplifying principles of the invention includes a steam path 2, in which a steam turbine 3 and a steam generator 4 are arranged. In this case, the steam turbine 3 is located downstream of the steam generator 4 and for example can drive a generator 5 so that the steam turbine installation 1 preferably serves for electricity generation. The steam turbine installation 1 can be a part of a combined cycle plant, that is to say a combined gas turbine-steam power plant. In particular, the steam generator 4 can then be heated with hot exhaust gases of the gas turbine. In principle, however, the heating of the steam generator 4 is designed in any desired manner.

According to an exemplary embodiment of the invention, an inertial separator 6 is arranged in the steam path 2 downstream of the steam generator 4 and upstream of the steam turbine 3. The inertial separator 6 serves for separating out particles, that is to say as a rule solid bodies, which are entrained in the steam flow, which is carried out by means of inertia forces. The separated-out particles can be extracted from the inertial separator 6 in accordance with an arrow 7.

In steam turbine installations 1 with a plurality of passages through the steam generator 4, so-called reheating, as are customary nowadays typically both upstream of the high-pressure turbine cylinder and of the intermediate-pressure turbine cylinder, such an inertial separator can be associated with each passage. In principle, each steam outlet from the steam generator 4 can be equipped with such an inertial separator 6.

In accordance with FIGS. 2 and 3, the inertial separator 6 can preferably be designed as a cyclone separator which is characterized in that the steam flow, which is represented by arrows 8 in FIG. 2, rotates around a longitudinal center axis 9 of the inertial separator 6. The cyclone separator is subsequently also designated with 6. Other constructional forms, such as electrostatic filters, are also possible so that the cyclone separator 6 which is mentioned here is quoted purely exemplarily and without limitation of the generality.

In the case of the embodiment which is shown in FIG. 2, the cyclone separator 6 in the installed state is preferably arranged in an upright position, as a result of which its longitudinal center axis 9 extends essentially vertically. The cyclone separator 6 has two sections in the vertical direction, that is to say an upper cylinder section 10 and a lower cone section 11. The cone section 11 adjoins the cylinder section 10 at the bottom and tapers as distance increases from the cylinder section 10, that is to say downwards.

The cyclone separator 6 is integrated into the steam path 2 via a steam inlet 12 and a steam outlet 13. In the case of the preferred embodiment which is shown here, the steam inlet 12 is connected tangentially to the cyclone separator 6 or to its cylinder section 10. As a result of this, the desired swirled flow with regard to the longitudinal center axis 9 is already forced during inflow into the cyclone separator 6. Such a swirled flow creates strong centrifugal forces. Entrained particles are thrown against the wall of the cyclone separator 6 on account of their increased mass inertia, as a result of which the particles for one thing can be sharply braked and for another thing can also be broken up. The braking of the particles leads to these being able to fall more easily downwards into the cone section 11 as a result of gravity force. The breaking down of the particles has the advantage that particles, which despite the intense separating effect of the cyclone separator 6 leave the cyclone separator 6 again with the steam flow 8, represent only a reduced risk of erosion in the steam turbine 3 for its blades.

As a result of the central swirl in the cyclone separator 6, a centrifugal field is created in this, in which particles with greater mass or greater specific weight are carried outwards. On the outside, the wall contact then takes place with the aforementioned consequences. In order to improve the breaking-down effect when the particles impinge upon the wall of the cyclone separator 6, the wall can be correspondingly designed. Furthermore, the wall of the cyclone separator 6 can preferably be designed specifically in the cylinder section 10 so that particles, which move along the wall, cannot reach the steam outlet 13. For example, the wall contains radially inwards projecting annular obstacles, which are not shown. It is optionally or alternatively also possible to electrostatically or electrodynamically charge the respective wall which also makes it possible to “catch” particles on the wall.

The cone section 11 serves as a collecting vessel for separated particles. The separated particles can be extracted from the cone section 11 in accordance with the arrow 7. This is basically possible during the operation of the steam turbine installation 1, since the steam flow operates with relatively high pressures. By means of cyclic opening of a corresponding blow-off valve, which is not shown here, which controls an outlet opening 14 of the cone section 11, the deposited particles can be discharged. It is also possible to utilize downtimes of the steam turbine installation 1 for removing the separated particles from the cone section 11.

In the case of the embodiment which is shown here, the steam outlet 13 is connected tangentially to the cyclone separator 6 or to its cylinder section 10. This tangential connection, which moreover is oriented in the rotational direction of the swirled flow, reduces the throughflow resistance or the pressure drop when exposing the cyclone separator 6 to throughflow. So that the entrained particles cannot flow through the cyclone separator 6 unhindered, the two tangentially arranged connections, that is to say steam inlet 12 and steam outlet 13, are arranged in a manner in which they are at a distance from each other in the axial direction. In this case, the arrangement which is shown here is preferred, in which the steam inlet 12 is arranged in a lower end region of the cylinder section 10, whereas the steam outlet 13 is arranged in an upper end region of the cylinder section 10. In order to reach the upper end region from the lower end region the entrained particles would have to migrate upwards against gravity force, which as a rule is not the case.

Unlike the embodiment which is shown, it is also possible in principle to again arrange the steam outlet 13 tangentially but in the opposite direction with regard to the rotational direction. Similarly, the steam outlet 13 can be radially oriented with regard to the longitudinal center axis 9. Furthermore, it is possible in principle to arrange the steam outlet 13 axially and centrally with regard to the longitudinal center axis 9. The last-named variant in this case has the greatest separating effect.

The inertial separator 6 is adapted to the particular operating conditions of the steam turbine installation 1. For this purpose, the inertial separator 6 is preferably designed so that it can operate at a steam pressure of between 250 bar and 350 bar. Furthermore, the inertial separator 6 is designed for steam temperatures in the range of 620° C. to 720° C. The dimensioning of the inertial separator 6 for example is selected so that as a result a steam quantity which is required for generating a steam turbine output of about 1000 MW can to a greater or lesser extent be cleaned of particles. For example, the inertial separator 6 is designed so that particles with a grain size of between 0.1 mm and 0.5 mm can be separated out from the steam. The material selection for the production of the inertial separator 6 is expediently to be selected so that it is suitable for separating out oxide particles such as magnetite or spinel. Furthermore, the inertial separator 6 should have a service life of at least 50 000 h, but preferably 100 000 h to 200 000 h.

According to FIG. 3, the inertial separator 6, which is designed as a cyclone separator 6, in another embodiment can have a globular or spherical housing 15 which can be particularly simply designed in an especially pressure-stable manner. The steam inlet 12 can also be connected tangentially to the housing 15 in this case. The connection of the steam inlet 12 to the housing 15 is preferably created in an equatorial plane 16 of the housing 15. In the case of the preferred upright arrangement of the cyclone separator 6 or of the housing 15, the equatorial plane 16 extends essentially horizontally.

The steam outlet 13, in the case of the upright housing 15, is preferably arranged at the top, in fact especially coaxially to the longitudinal center axis 9 of the housing 15. The longitudinal center axes of the globular housing 15 are characterized in that they all extend through the middle point of the housing 15, which is not described in more detail. In the case of the upright housing 15, the longitudinal center axis 9 which is associated with the steam outlet 13 extends essentially vertically. In the preferred embodiment which is shown here the longitudinal center axis 9 which is associated with the steam outlet 13 is perpendicular to the previously mentioned equatorial plane 16 which is associated with the steam inlet 12.

The outlet opening 14, in the case of the upright arrangement of the housing 15, is preferably located at the lower end of the housing 15. In the preferred embodiment which is shown, the outlet opening 14 is arranged on the housing 15 coaxially to a longitudinal center axis 9′ of the housing 15. In the present embodiment, the longitudinal center axis 9′ which is associated with the outlet opening 14 is arranged coaxially to the longitudinal center axis 9 which is associated with the steam outlet 13, i.e., the two longitudinal center axes 9 and 9′ coincide. Therefore, in the present case the longitudinal center axis 9′, which is associated with the outlet opening 14, is also perpendicular to the equatorial plane 16 and extends essentially vertically.

LIST OF DESIGNATIONS

-   -   1 Steam turbine installation     -   2 Steam path     -   3 Steam turbine     -   4 Steam generator     -   5 Generator     -   6 Inertial separator/cyclone separator     -   7 Separated particles     -   8 Steam flow     -   9, 9′ Longitudinal center axis of 6     -   10 Cylinder section of 6     -   11 Cone section of 6     -   12 Steam inlet     -   13 Steam outlet     -   14 Outlet opening of 11 or 15     -   15 Housing     -   16 Equatorial plane

While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein. 

1. A steam turbine installation useful for electricity generation comprising: a steam path; a steam generator and a steam turbine arranged in the steam path, the steam turbine downstream of the steam generator; and at least one inertial separator arranged in the steam path between the steam generator and the steam turbine.
 2. The steam turbine installation as claimed in claim 1, wherein the inertial separator comprises a cyclone separator.
 3. The steam turbine installation as claimed in claim 2, comprising at least one the following: the cyclone separator is arranged in an upright position and has a vertical longitudinal center axis; a steam inlet connected tangentially to the cyclone separator; a steam outlet connected axially centrally or tangentially to the cyclone separator; the cyclone separator includes a cylinder section with a lower end region, a steam inlet connected to the cyclone separator lower end region; the cyclone separator includes a cylinder section with an upper end region, a steam outlet connected to the cyclone separator upper end region; the cyclone separator includes a cylinder section with a bottom, and a downwards tapering cone section which adjoins the cylinder section at the bottom.
 4. The steam turbine installation as claimed in claim 2, comprising at least one of the following: the cyclone separator has a globular housing; the cyclone separator has a housing, and comprising a steam inlet connected tangentially to the housing; the cyclone separator has a housing, and comprising a steam inlet connected to the housing in an equatorial plane; the cyclone separator has a housing with a longitudinal center axis, and comprising a steam outlet connected to the housing coaxially to the longitudinal center axis of the housing; the cyclone separator has a steam inlet, a steam outlet, and a longitudinal center axis associated with the steam outlet is perpendicular to an equatorial plane associated with the steam inlet; the cyclone separator has a steam outlet, a longitudinal center axis, and an outlet opening for removing contaminants from the housing which are deposited in the housing arranged on the housing coaxially to the longitudinal center axis of the housing; the cyclone separator has a steam outlet, a longitudinal center axis, and a longitudinal center axis associated with the outlet opening arranged coaxially to a longitudinal center axis associated with the steam outlet; the cyclone separator has a steam inlet, a steam outlet opening, and a longitudinal center axis associated with the outlet opening perpendicular to an equatorial plane which is associated with the steam inlet; and the cyclone separator has a steam inlet, a steam outlet opening, and a housing arranged in the upright position so that an equatorial plane associated with the steam inlet extends essentially horizontally, and/or so that a longitudinal center axis associated with the steam outlet extends vertically, and/or so that a longitudinal center axis associated with the outlet opening extends vertically.
 5. The steam turbine installation as claimed in claim 1, comprising at least one of the following: the inertial separator is configured and arranged to be operated at a steam pressure of about 250 bar to about 350 bar, and/or at a steam temperature of about 620° C. to about 720° C.; the inertial separator is configured and arranged to separate out from the steam particles with a grain size of less than 0.5 mm; and the inertial separator is configured and arranged to separate out oxide particles.
 6. The steam turbine installation as claimed in claim 5, wherein the inertial separator is configured and arranged to separate out from the steam particles with a grain size of less than 0.1 mm.
 7. The steam turbine installation as claimed in claim 5, wherein the oxide particles comprises magnetite or spinel.
 8. A method for operating a steam turbine installation for electricity generation, the method comprising: guiding steam from a steam generator to a steam turbine; and extracting from the steam particles which are entrained upstream of the steam turbine.
 9. The method as claimed in claim 8, wherein extracting comprises separating out particles from the steam with inertia forces. 